Long Continuous Run Internal Combustion Engines

Internal Combustion Engines

Internal Combustion Engines

Charles L. ProctorII, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

II Categories

Internal combustion engines can be divided into two categories: continuous-combustion engines and intermittent-combustion engines. The continuous-combustion engine is characterized by a steady flow of fuel and air into the engine and a stable flame maintained within the engine. Gas turbine engines exemplify the continuous-combustion engine. The intermittent-combustion engine is characterized by periodic ignition of fuel and air. Commonly referred to as reciprocating engines, these devices process discrete volumes of air and fuel in a cyclic manner. Gasoline piston engines and diesel engines are examples of this group.

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Life Cycle Tribology

A. Morina , ... M. Priest , in Tribology and Interface Engineering Series, 2005

1 INTRODUCTION

Internal combustion engine fuel efficiency can be increased by reducing the mechanical losses primarily caused by friction. The use of appropriate oils reduces friction, increases fuel efficiency and at the same time maintains low wear. There are two approaches by which friction reduction in internal combustion engines can be achieved: by reducing the viscosity of the oil which leads to lower friction in the fluid film lubrication regime and by using friction-reducing additives which minimise friction in the mixed/boundary lubrication regime when surface asperities come into contact [ 1].

A very important class of friction-reducing additives, used extensively in crankcase oil formulations, are the molybdenum-containing compounds such as molybdenum dialkyldithiocarbamate (MoDTC). The total additive package amount in the oil can be in the range of 5–25% [2] and the effectiveness of MoDTC in reducing friction is strongly affected by synergistic or antagonistic effects with other additives, especially zinc dialkyldithiophosphate (ZDDP) [3–5]. The ZDDP additive, besides having anti-oxidant properties, is known to be very effective in protecting the surfaces from wear under boundary lubrication conditions; properties that make it an essential ingredient in the vast majority of current oil formulations [6]. As two of the key components in oils, understanding the interactions between ZDDP and MoDTC in tribological performance is therefore essential for achieving optimum performance. Previous work [7] has also identified that improvements must be made to valve train lubrication mathematical models to improve their sensitivity to oil formulation characteristics. Only through developing a better understanding of tribofilm formation, structure, chemical and morphological properties, and correlating them to running-in of valve train systems, will such improvements be possible.

MoDTC is documented to reduce friction by forming an MoS₂ — containing film on metal surfaces [8–12]. The friction was seen to be reduced after a certain time, defined as the induction phase, after which the friction dropped from high values of around 0.12 to the reduced values in the order of 0.05. Yamamoto and Gondo [9, 13, 14], in their work using X-ray Photoelectron Spectroscopy (XPS), suggested that the formation of MoS₂ requires the preliminary formation of an MoO₃ layer. The formation of M0S₂ from MoDTC was seen to be as a result of solid-solid contact [15]. Formation of the MoO₃ prior to any friction drop suggests that an increase in roughness would occur which could promote formation of M0S2, indicating a physical effect of MoO₃ in the formation of M0S₂. Although in several works [9, 11, 15], MoDTC alone was shown to be effective in friction reduction, there are reports that show MoDTC can be effective in friction reduction only in the presence of the ZDDP additive [3–5]. Sogawa et al. [16] showed that the presence of ZDDP helps the formation of M0S₂ from MoDTC. They found, when a model oil containing both ZDDP and MoDTC was used, that about 40% of S from ZDDP was used to form the M0S₂ tribofilm in the wear scar, but the precise mechanism was not explored. On the other hand, Martin et al. [17] proposed a reaction of M0O3 elimination by Zn phosphate, generated from ZDDP, according to the Hard and Soft Acid and Bases (HSAB) principle. The elimination of M0O₃ was thought to be the reason why a ZDDP/MoDTC system is more effective in reducing friction than MoDTC alone — a chemical effect of ZDDP in MoDTC friction reduction performance. However, the topographical analyses of the ZDDP tribofilms have verified the high roughness of this film [18, 19] — indicative of the ZDDP influence on M0S₂ formation being of a physical nature.

Although an indication of the species formed when the MoDTC additive is used can be obtained from reviewing the work done by several groups, the reaction sequence by which MoDTC forms M0S₂ has not yet been established or proven experimentally. Also, the effect of ZDDP on the M0S₂ formation mechanism from MoDTC is still not fully understood. In the present paper a full characterisation, in term of chemical and topographical properties, of the tribofilms formed prior to the friction drop is presented and the conditions favourable for M0S₂ formation and consequently friction reduction are discussed. A test procedure involving changing the oil from one model oil to another has been used in order to understand if the ZDDP/MoDTC interactions are of a physical or chemical nature or a combination of both.

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Cleaner Vehicle Emissions

A.P.E. York , A. Tsolakis , in Encyclopedia of Materials: Science and Technology, 2010

1 Introduction

The internal combustion (IC) engine is the most efficient and reliable power plant in the transportation (petrol and diesel engines) and heavy machinery (diesel engine) sector. IC engines are expected to be around until: (i) fuel shortages become a serious issue; (ii) new, less-polluting, and more-efficient technologies are developed as a replacement; or (iii) emissions regulations, set by environmental agencies to improve air quality, become unachievable by the engine and vehicle manufacturers.

Since the 1970s, catalytic emission control technologies for the automotive industry have been developed, in parallel with engine and fuel technologies, initially to control CO, HC, and NO _x emissions from petrol engines. Today, emission regulations have also been established in diesel engines to reduce particulate matter (PM), in addition to the other three pollutants. Further, emission regulations are periodically updated with new pollutants, such as the greenhouse gases CH₄ and CO₂, or criteria, for example, particulate size and number, being added.

Concerns over CO₂ greenhouse emissions, and fuel security issues, have seen the rise in the development of vehicles with much-improved fuel economy, that is, lightweight vehicles, hybrids, and vehicles with diesel engines. Nevertheless, in present applications, catalytic converters have been adopted as the main approach for pollution control. Significant progress has been made in developing these technologies and the catalytic materials required.

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Tribochemistry of Lubricating Oils

In Tribology and Interface Engineering Series, 2003

The mechanism of action of surfactant additives.

The operation of internal combustion (IC) engines results in the formation of by-products: gases, soot particles, acids, water and free radical sources.

A portion of these by-products enters the crankcase via blow-by gases and adsorption in the thin lubricant film. It seems that these mechanisms are partly dependent on the degree of aggregation of additives in the base oil. It has been demonstrated that in a fresh oil, detergent additives take the form of reverse micelles in equilibrium with the saturated monomer solution. Depending on their chemistry, they are involved in solubilization, neutralization and adsorption (Pawlak, 2001; Sakurai, 1981).

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Fuel Chemistry

Sarma V. Pisupadti , in Encyclopedia of Physical Science and Technology (Third Edition), 2003

XII.C Gas Turbines

Another class of internal combustion engine is the gas turbine. Air is compressed to high pressures (10–30   atm) in a centrifugal compressor. Fuel is sprayed into the primary combustion zone where the fuel burns and increases the temerpature of the gases. The gas volume increases with combustion and the gases expand though a turbine. The power generated exceeds that required for the compressor. This drives the shaft to run an electric generator. In the aircraft applications, the gases are released at high velocity to provide the thrust. These systems are light weight compared to land-based systems. Land-based systems use either distillate oil or natural gas. Gas turbine-based power generation is used commonly to meet the peak power requirements rather than for base load operation.

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ABSORBERS, VIBRATION

V. SteffenJr., D. Rade , in Encyclopedia of Vibration, 2001

Torsional Dynamic Vibration Absorbers

Torsional vibrations of internal combustion engines and other rotating systems can be controlled by using torsional vibration absorbers. Such an arrangement is shown in Figure 13A. The primary system is represented by inertia J _p and torsional stiffness k_{T p}, and the absorber is represented by inertia J _a and torsional stiffness k_{T a}. Viscous damping is provided by oil inside a housing rigidly connected to the primary system, in such a way that a dissipative torque given by $c_{\text{T}}({\stackrel{.}{\theta }}_{\text{p}}-{\stackrel{.}{\theta }}_{\text{a}})$ is generated. An equivalent translational two-degree-of-freedom system is shown in Figure 13B. Since the dynamic equations of motion are similar for both systems, the formulae obtained for the translational DVA and the procedure to obtain its optimal design remain applicable for the torsional system. The equivalence between the parameters of the translational and torsional systems is indicated in Table 4.

Figure 13. (A) Scheme of a torsional system with DVA and (B) equivalent rectilinear system.

Table 4. Equivalence between translational and torsional parameters

	Translational system	Torsional System
Inertia of the primary system	m p (kg)	J p (kgm2)
Stiffness of the primary System	k p (Nm−1)	k T (Nmrad−1)
Inertia of the DVA	m a (kg)	J a (kgm2)
Stiffness of the DVA	Ka (Nm−1)	k Ta (N.mrad−1)
Damping of the DVA	C a (N.sm−1)	c Ta (N.m.srad−1)

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Automotive Engine Materials

R.C. McCune , G.A. Weber , in Encyclopedia of Materials: Science and Technology, 2001

2.7 Air and Fuel Handling

The schematized modern internal combustion engine shown in Fig. 2, illustrates the use of an advanced air intake manifold, in which the complex channels for directing air into the individual cylinders are formed by molding the part using Nylon 6,6 (Palmer et al. 1996), with use of a vibrational welding process to join two halves of the manifold. This manufacturing technique allows for weight reduction and more complex manifolds than could be fabricated from aluminum die or sand casting, which are alternate methods. The ability to have extraordinary control over the introduction of fuel into the intake manifold is presently achieved through the use of fuel injectors, which are electromagnetically controlled valves operating under pressurization of the fuel. The injector is a critical part of diesel or compression ignition engines, and is being advanced in extreme pressure versions for direct cylinder injection in gasoline direct-injection (GDI) or direct-injection spark-ignition (DISI) engines. Injectors employ advanced, heat treatable stainless steels such as the 440 series for internal parts, and often use advanced physical-vapor deposition coatings such as titanium nitride (TiN) to minimize corrosion, erosion, or sub-component seizure.

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THERMAL BOUNDARY LAYER MEASUREMENTS USING A MULTIPLE THIN WIRE RESISTANCE THERMOMETER IN AN INTERNAL COMBUSTION ENGINE

A.Demir Bayka , in Experimental Heat Transfer, Fluid Mechanics and Thermodynamics 1993, 1993

INTRODUCTION

Heat transfer in internal combustion engines, influences the volumetric, mechanical and thermal efficiencies, the exhaust emissions, choice of materials, dimensioning of engine components and maintenance costs. It is a major parameter in the simulation of the thermodynamic processes. The finite element techniques for assisting the design of engine components are also affected by heat transfer due to thermal loading of the components. Approximately 20% of the available energy is lost by heat transfer during various thermodynamic processes. The local heat transfer in the cylinder affects the mechanical strength of the piston or rings as well as the viscosity of the lubricating oil and the possibility of abnormal combustion. Flame nucleus formation, spark plug or exhaust valve performance depend on heat transfer. When designing the cylinder head and piston or broadly the combustion chamber, the effect of material, dimensioning, shape and configuration on heat transfer are predicted. The performance, endurance and stability of the manufactured product is closely related to the success of the predictions.

There are two aspects of heat transfer; the overall mean heat transfer affects the overall performance of the engine while the instantaneous, local heat transfer affects the problem areas in the design. Therefore, experimental and theoretical work has been equally focused on mean and local, instantaneous heat transfer.

Heat transfer between the gases and cylinder walls of internal combustion engines is by forced convection and radiation. Radiation heat transfer can be neglected in spark ignition engines. However, it can account for 20 to 40 percent of the overall heat transfer in compression ignition engines. This is due to the presence of soot particles in compression ignition engine combustion.

The prediction of overall heat transfer in internal combustion engines is usually based on the assumption that the heat transfer process is quasi-steady. Various empirical relations have been formulated for predicting spatially averaged instantaneous heat transfer. Annand[1] proposed to calculate the quasi-steady heat transfer in spark ignition engines by convective heat transfer;

(1) $\frac{{\text{q}}_{\text{c}}}{\text{A}}={\text{h}}_{\text{c}}\text{.}{\text{(T}}_{\text{g}}\text{-}{\text{T}}_{\text{w}}\text{)}$

After applying dimensional analysis he proposed a dimensionless relationship;

(2) $\text{Nu}\text{=}\text{a}{\text{.Re}}^{\text{b}}$

(3) $\frac{{\text{h}}_{\text{c}}\text{.D}}{\text{k}}=\text{a}\text{.}{\left(\frac{{}^{\text{ρ}\text{.v}}{\text{pm}}^{.\text{D}}}{\text{μ}}\right)}^{\text{b}}$

the cylinder bore diameter was taken as the characteristic dimension and the mean piston velocity was used to represent the gas motion. Armand also proposed an empirical relation for radiation heat transfer;

(4) $\frac{{\text{q}}_{\text{r}}}{\text{A}}=\text{c}\text{.ε}\text{.}{\text{(T}}_{\text{g}}^{\text{4}}-{\text{T}}_{\text{w}}^4)$

and combined with Eq. (1) and Eq. (3);

(5) $\begin{array}{l}\frac{\text{q}}{\text{A}}=\frac{\text{k}}{\text{D}}.\text{a}\text{.}{\left(\frac{{}^{\text{ρ}\text{.v}}{\text{pm}}^{.\text{D}}}{\text{μ}}\right)}^{\text{b}}.({\text{T}}_{\text{g}}-{\text{T}}_{\text{w}})\\ +\text{c}\text{.ε}\text{.}{\text{(T}}_{\text{g}}^{\text{4}}-{\text{T}}_{\text{w}}^4)\end{array}$

where a = 0.35 to 0.8b = 0.7c = 0 spark ignition enginesc = 0.57 compression ignition engines

Woschni[2] proposed a similar relation to Eq. (2) with a = 0.035 and b = 0.8. In order to get a better fit to his experimental data Hohenburg[3] further modified the effective gas velocity term and used the instantaneous cylinder volume to define the characteristic length. In an attempt to predict local heat fluxes and to take into account the local effect of swirl in direct injection compression ignition engines, Dent and Sulaiman[4] proposed the following relationship;

(6) $\frac{\text{q}}{\text{A}}=0.023\frac{\text{k}}{\text{r}}.\left(\frac{\text{ρ}\text{.}\text{ω}\text{.}{\text{r}}^2}{\text{μ}}\right){.}^{0.8}({\text{T}}_{\text{g}}-{\text{T}}_{\text{w}})$

for the Prandtl number Pr = 0.73, T_g and T_w are local temperatures at equal radii from the point of injection.

In spark ignition engines two zone or multizone models are used for describing the combustion process. Annand's and Woschni's area averaged instantaneous heat flux predictions are used with mass averaged zonal mean temperatures.

The accuracy of the predictions of the instantaneous heat transfer rate depends mainly on the accuracy of the surface wall temperature measurements. The pioneering work of Eichelberg[5] was based on the results obtained from thermocouple junctions of thin wires located below the cylinder head surface. The surface temperature measurements improved with the use of deposition of metals under vacuum.

The Bendersky[6] thermocouple, shown in Fig. 1 was a stand alone probe which could be fitted into the cylinder head. It suffered from contact resistance at the threading and from the direct interference of the nickel wire at the center of the thermocouple hot junction with the homogeneity of the probe body. The insulation of the nickel wire also posed a problem which was cured by a capacitive discharge technique. The basic idea however, was elaborated by various researchers. Ma[7] used a composite strip as a lead from the thermocouple junction. Bayka[8] used a similar technique for manufacturing surface thermocouples (Fig. 2). The vacuum deposition technique was also used for manufacturing heat flux metering probes. Dao et.al.[9] deposited thermistors on both surfaces of thin pyrex discs. Alkidas[10] also used heat flux probes. In spark ignition engines measurement of the surface temperatures at various distances from the spark plug indicated a higher heat flux at the early flame arrival zone. This was in accordance with gas temperature predictions of a multizone model proposed by Bayka[11].

Figure 1. Bendersky surface thermocouple

Figure 2. Bayka surface thermocouple

The weakest aspect of convective heat transfer predictions is the incorporation of the gas motion into the Reynolds number in Eq. (2).

The gas temperature can be visualized as having a steep gradient near the cylinder walls within the thermal boundary layer and having an almost zero gradient away from the cylinder walls. Bayka[12] applied this model separately to the burned and the unburned gas with a flame front separating the two zones, for the combustion process in a single stroke rapid compression machine. The same formulation can also be applied to a multizone model as well. Predicting the thermal boundary layer thickness and evaluating an effective thermal conductivity for the thermal boundary layer can be used to predict the heat flux. Borgnakke et.al.[13] proposed a model for predicting heat fluxes through the thermal boundary and turbulence in the cylinder. The heat flux through the thermal boundary layer could be expressed as :

(7) $\frac{\text{q}}{\text{A}}=\frac{{}^{\text{k}}\text{e}}{\text{δ}}.({\text{T}}_{\text{g}}-{\text{T}}_{\text{w}})$

The thermal boundary layer thickness will vary during the gas exchange, compression, combustion and expansion processes. It will be affected by the engine speed, load, air/fuel ratio, induction or compression induced swirl, the inlet gas temperature, the volumetric efficiency, the compression ratio, spark or injection timing and by the condition of the coolant. The combustion chamber design, wall thicknesses and materials of the cylinder head, liner and piston will also affect the thermal boundary layer. Lyford-Pike and Heywood[14] made measurements of the thermal boundary layer thickness in a spark ignition engine by Schlieren photography.

The purpose of this study was to manufacture a stand alone probe and data acquisition system for collecting experimental data on the thermal boundary layer of the gases over the surface, as well as the local surface temperature of the cylinder head of a reciprocating internal combustion engine. This phase of the study was focused on successfully operating the probe and the data acquisition system. A further study is being made in which the one dimensional model developed by Bayka[12] is elaborated and additional parameters such as engine speed and gas swirl are investigated.

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Automotive Control Systems

Uwe Kiencke , in Encyclopedia of Physical Science and Technology (Third Edition), 2003

I Potential of Alternate Fuels and Propulsion Systems

Today's vehicles primarily employ internal-combustion engines. We will begin our discussion here by investigating alternate fuels and propulsion systems. In Fig. 1, the relative energy requirements to move a vehicle 100 km are shown for different propulsion systems. Electrical drives have been available for more than 100 years, but energy/fuel storage is a problem. Standard lead batteries are much too heavy for energy storage. Other typers of batteries are lighter, but they are still not comparable to the weight of ordinary fuel. Power is dissipated in the charging and discharging process of the battery, reducing the overall efficiency. Eventually, battery-driven vehicles with a reduced buffer size may be used in special applications at short distances. Another promising approach is hybrid vehicles, in which an internal-combustion engine is combined with an electrical motor. The electrical motor may be activated to smooth out transients of the combustion engine and the driveline, contributing to reduced noxious emissions. Under part-load conditions, the combustion engine can also load the battery, so that battery volume and weight are significantly reduced.

FIGURE 1. Energy demand of different engine concepts. [Adapted from Ledjeff, K. (1995). "Brennstoffzellen: Entwicklung, Technologie, Anwendung" Müller, Heidelberg.]

Hydrogen (H₂) gas is too voluminous to be used directly as an adequate energy source. It can by stored either at an extremely cold temperature of 20   K or at a relatively high pressure at room temperature. Over long time periods, H₂ leaks through even thick-walled steel tanks. In hydride buffers, H₂ is chemically bound. Since hydrogen burns at high combustion temperatures, emissions of nitrogen oxyde (NO _x ) become a problem.

Fuel cells produce electrical energy directly at low temperatures. Thermal efficiencies of 70% are reached for the synthesis of H₂ and O₂. The storage of hydrogen is again a problem. If H₂ must be generated from natural gas or from methanol, efficiencies become much lower. The task is to generate the exact amount of hydrogen from, for example, methanol even under real-time transient drive conditions. For this, the fuel conversion process can be modeled, and the actual masses reacting in the conversion process can be estimated in real time, as a basis for state space control. Fuel cells appear to be a promising alternative to combustion engines. Table I illustrates that the weight and volume of stored fuel vary a lot. It can be understood, then, why gasoline or diesel fuels are dominating today's propulsion systems.

TABLE I. Typical Storage Volumes and Weights of Different Energy Sources with an Energy of 1000   kWh

	Volume	Mass	Tank	Mass+Tank
Source	V(l)	m 1 (kg)	m 2 (kg)	m 1   + m 2 (kg)
Fuel	117	83	21	104
Diesel	102	85	17	102
Methanol	224	180	41	221
Liquid gas	153	78	90	168
Methane	259	72	500	570
H2, liquid	426	30	142	172
H2, hydride buffer	200	30	970	1000
Battery (lead)	5000	0	10,000	10,000

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Nanoparticle Technologies

Farid Bensebaa , in Interface Science and Technology, 2013

2.5 NO _x Decomposition

NO _x emissions from internal combustion engines and other industrial activities are significant contributors to air pollution. Smog is omnipresent in the majority of big cities of industrialized countries. It is directly related to nitrogen oxides, ozone, and hydrocarbon emissions from car exhaust. A nitrate smog component has been shown to be very detrimental to health and can increase the death rate among the elderly. Supported NP catalysts have been shown to significantly reduce NO _x emissions. A typical car exhaust catalyst contains a monolith support with a washcoat impregnated with precious metal NPs as active catalysts [52].

Noble metal-based catalytic decomposition of NO _x is widely used. Solid oxide electrochemical reactors can provide some advantage in decomposing NO _x [53]. The combination of a 2D cathode structure and NiO NPs was effectively used to improve the efficiency of the NO _x -to-NO₂ conversion (Fig. 8.3). Nickel-based grain sizes are about 10–50   nm. Low energy consumption and operation under excess oxygen content are achieved using this approach. Two porous electrodes sandwiching an oxygen ion solid electrolyte were used to effectively transform NO _x to N₂ with a high yield rate (Fig. 8.3). In addition, this design is scalable.

Figure 8.3. Solid oxide electrochemical cell and NO _x decomposition on a single-layered cathode [53].

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