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Two charge-air cooling turbo-charging systems, named Turbo-Cool and T2C, have been introduced. Turbo-Cool employs an air turbine expander/suction-compressor unit in the intake side and a VGT in the exhaust side, while T2C employs an air turbine expansion in the intake side and an exhaust VGT with a same shaft with the air turbine. A Nissan SR20DET turbocharged gasoline engine with the two charge-air cooling turbo-charging systems have been modeled using GT-SUITE 6.0 engine simulation code. Modeling results show that either Turbo-Cool or T2C must be combined with exhaust VGT. The air turbine in both systems can be either VGT or fixed. Modeling results also show that the power at WOT and rated engine speed of the engine with the proposed charge-air cooling turbo-charging systems can be increased by 20∼30%, the maximum torque at WOT can be increased by 46∼71%, and the BSFC at WOT and rated engine speed can be decreased by 4∼5%.

A newly developed turbocharging system, named MIXPC, is proposed and the performance of the proposed system applied to diesel engines is evaluated. The aim of this proposed system is to reduce the scavenging interference between cylinders, and to lower the pumping loss in cylinders and the brake specific fuel consumption. In addition, exhaust manifolds of simplified design can be constructed with small dimensions, low weight and a single turbine entry. A simulation code based on a second-order FVM+TVD (finite volume method + total variation diminishing) is developed and used to simulate engines with MIXPC. By simulating a 16V280ZJG diesel engine using the MPC turbocharging system and MIXPC, it is found that not only the average scavenging coefficient of MIXPC is larger than that of MPC, but also cylinders of MIXPC have more homogeneous scavenging coefficients than that of MPC, and the pumping loss and BSFC of MIXPC are lower than those of MPC.

The significant fuel-economy gain that may be achieved from the application of ceramic materials to the piston engine technology requires practical and reliable exhaust heat recovery means. Such a means has so far eluded the engine technology community. The “add-on” bottoming cycles to the traditional piston engines based on Otto cycle and Diesel cycle are totally impractical. By contrast, steam injection has been effectively applied to gas turbine (electric generator) systems with significant increase in power output and thermal efficiency. The steam-injected gas turbine has been increasingly adopted in power production, and can be regarded as a mature technology. The question then arises as to whether steam injection can be used for piston-type engines in transportation. Gas generator engines-which have been investigated as experimental engines for many years-may be one of the piston-type engines ideally suited for practical heat recovery.

The current concern over engine emission motivates us to reconsider the continuous-combustion option, which was first adopted by Brayton in the 1870's, with disappointing fuel economy in comparison with the Otto four-stroke. The two-part cycle principle of the gas generator engine was proposed by Wang & Jeng (1992). In this paper, a continuous-combustion gas generator engine is investigated using zero-dimensional modeling. The result confirms the validity of the two-part cycle principle producing simultaneous increase in power output and thermal efficiency. However, the various irreversible losses of the continuous-combustion piston unit result in unsatisfactory thermal efficiency. The continuous-combustion gas generator engine is, therefore, not a viable concept in its basic form. The alternative, intermittent-combustion gas generator engine is expected to sustain smaller irreversible losses; its performance prediction remains to be studied.

A new internal combustion engine is proposed. This engine is one example of gas generator engines, configured according to a newly proposed cycle principle. Turbocharging with intercooling is employed to reduce the energy loss of engine exhaust. A reciprocating piston-gasifier is used to further boost the pressure and to raise the turbine inlet temperature near its material limit. To study the feasibility of the proposed engine, a piston-gasifier is designed to consist of manifolds and pairs of cylinders with different bores. To simulate the operations of the piston-gasifier, a numerical model is developed. The manifolds and cylinders are treated as open systems and combustion is described as a one-zone heat release process. Subprocesses are described in sufficient detail. The operating characteristics of the piston-gasifier are predicted and analyzes over a broad range of operating parameters.

In the first part of this two-part article, a piston-gasifier is designed, and its quasi-steady operating characteristics are predicted by a numerical model. The objective of this second part of article is to study the operating characteristics of the whole engine system. Intercoolers are designed, and their effectivenesses are solved by a combination of analytical solution and empirical correlations. The turbocharging compressors and turbine are described by steady state performance maps. The power turbine is described by the modified Stodola Ellipse with efficiency assumed constant. The numerical model matches the operations of all components to predict the performance of whole engine system. Utilizing the operating characteristics of the piston-gasifier, the cycle analysis of the whole engine system indicates that there is an optimum intake pressure of the piston-gasifier for each set of crankshaft speed and piston-gasifier exhaust temperature.

This paper makes the case for the gas generator engine - a type of compounded engines - as a potential future automotive engine. The existing gas generator engines are characterized by their mediocre performance and fuel economy. The case for the new gas generator engine is based on a proposed cycle principle, which achieves simultaneous improvements in thermal efficiency and power output/weight ratio. This very attractive engineering solution may transform the mediocre existing engines into new engines of exceptional promise, which merit serious consideration.