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Off-highway mining and construction equipment typically converts all the power output of the engine to hydraulic power, with this power then used to perform the earth-moving operations, and also to propel the vehicle. This equipment presents significant opportunities for a new type of powerplant designed to deliver hydraulic power directly. An alternative to the conventional engine driven pump is a free-piston engine-pump (FPEP). The FPEP incorporates the functions of both an internal combustion engine and a hydraulic pump into a single, less-complex unit. The design presented in this paper utilizes two double-ended, reciprocating, opposed pistons, with combustion at one end of each piston and pumping at the opposite end. The opposed piston layout provides balance and also facilitates uniflow scavenging through intake and exhaust ports in the combustion section of the engine. An important feature of this FPEP design is the rebound accumulator circuit.

The combustion mechanism in a Compression Ignition Homogeneous Charge (CIHC) engine was studied. Previous experiments done on a four-stroke CIHC engine were modeled using the KIVA-II code with modifications to the combustion, heat transfer, and crevice flow submodels. A laminar and turbulence characteristic time combustion model that has been used for spark-ignited engine studies was extended to allow predictions of ignition. The rate of conversion from one chemical species to another is modeled using a characteristic time which is the sum of a laminar (high temperature) chemistry time, an ignition (low temperature) chemistry time, and a turbulence mixing time. The ignition characteristic time was modeled using data from elementary initiation reactions and has the Arrhenius form. It was found to be possible to match all engine test cases reasonably well with one set of combustion model constants.

Diesel engine in-cylinder combustion processes have been studied using computational models with particular attention to spray development, vaporization, fuel/air mixture formation and combustion. A thermodynamic zero-dimensional cycle analysis program was used to determine initial conditions for the multidimensional calculations. A modified version of the time-dependent, three-dimensional computational fluid dynamics code KIVA-II was used for the computations, with a detailed treatment for the spray calculations and a simplified model for combustion. The calculations were used to obtain an understanding of the potential predictive capabilities of the models. It was found that there is a strong sensitivity of the results to numerical grid resolution. With proper grid resolution, the calculations were found to reproduce experimental data for non- vaporizing and vaporizing sprays. However, for vaporizing sprays with combustion, extremely fine grids are needed.

The modified hypocycloid (MH) mechanism, which uses gears to produce straight line motion, has been proposed as an alternative to the slider-crank mechanism for internal combustion (IC) engines. Advantages of the MH mechanism over the slider-crank for an IC engine include the capability of perfect balancing with any number of cylinders and the absence of piston side loads. The elimination of piston side load has the potential for lower piston friction, reduced piston slap, and less susceptibility to cylinder liner cavitation. To evaluate the concept, an experimental single cylinder four-stroke engine which utilizes the MH mechanism is currently being built at the University of Wisconsin-Madison. The MH engine has an increased number of friction interfaces compared to a conventional slider-crank engine due to additional bearings and the gear meshes. Thus, the lubrication of these components is an important issue in total MH engine friction.

It has long been known that IC engine variable valve timing (VVT) has the potential for significant improvements in engine performance. Many technical papers have been published on the potential benefits of internal combustion engine variable valve timing and the modes of valve operation that can be used to realize these benefits. Almost 800 US patents have been released on the subject of mechanisms to effect VVT since 1880. An extensive review of this literature and patents was made to determine the benefits obtainable from VVT and what operation modes allow these benefits to be obtained. We conclude that VVT has much potential. The potential gains include 15% or more average fuel economy gains as well as significant improvements in torque characteristics, emission reductions, etc. Nevertheless, little of VVT's potential has yet been realized, since serious mechanical difficulties have limited VVT applications to date.

Mechanisms for internal combustion engine variable valve timing (VVT) have been the subject of almost 800 US patents since 1880. Over 110 of these patents were issued just in the three years 1985 through 1987. Also, many technical papers have been published on VVT mechanisms. We reviewed all of these patents and much of the literature. As a result, we have classified all the mechanisms found into IS basic concepts which we describe and evaluate in this paper. We conclude that VVT has much potential, but that very little of this potential has yet been realized. Serious difficulties have limited the application of variable valve timing to date. Virtually all VVT mechanisms proposed until recently suffer from high cost and complexity, limited variability, and high impact velocities. An improved system is described in a companion paper (1)*.

Forage harvesting, processing and handling equipment research is currently underway which will improve commodity quality, produce “value -added” products from forages, reduce energy and labor requirements of the equipment and improve forage marketability. Technologies are described which could increase forage quality and value by removing it from the field sooner after it is mowed to minimize the risk of weather damage. Mechanisms and management strategies for reducing the labor and energy required for field processing and for improving the marketability of forages are also described.

Several recent papers describe closed loop fuel-air ratio control systems designed to operate at stoichiometric conditions because of the high three-way catalyst conversion efficiencies which occur only in a narrow band around stoichiometric. This paper investigates closed loop control of fuel-air ratio using a temperature compensated zirconia sensor at other than stoichiometric conditions. If engines can be made to run at very lean(Φ≈0.6-0.7) equivalence ratios through greater attention to proper fuel-air mixing and vaporization, CO, HC, and NOx emissions are minimized simultaneously. Closed loop control in the lean region makes the system insensitive to parameter variations and allows the fuel-air ratio to be maintained closer to the lean limit than would be possible under conventional open loop conditions.

This paper is concerned with a series of three important problems on reliability where complete solutions are still unavailable. These problems have all been researched and approximate solutions are outlined. The three areas of interest are 1. The government requirement of assurance of high reliability of complex items where the cost of sampling is extremely high. 2. Confidence intervals for a system in series where component data are available, and 3. Estimation of the parameters of the Weibull distribution when sampling terminates after the rth failure is observed in a sample of size n.