Composite load spectra for select space propulsion structural components

The objective of the Composite Load Spectra (CLS) project is to build a knowledge based system to synthesize probabilistic loads for selected space propulsion engine components. The knowledge based system has a load expert system module and a load calculation module. The load expert system provides load information and the load calculation module generates the probabilistic load distributions. The engine loads are divided into 4 broad classes: the engine independent loads, the engine system dependent load, the component local independent loads and the component loads. These classes are defined and illustrated

Investigation of cylinder deactivation and variable valve actuation on gasoline engine performance

Increasingly stringent regulations on gasoline engine fuel consumption and exhaust emissions require additional technology integration such as Cylinder Deactivation (CDA) and Variable valve actuation (VVA) to improve part load engine efficiency. At part load, CDA is achieved by closing the inlet and exhaust valves and shutting off the fuel supply to a selected number of cylinders. Variable valve actuation (VVA) enables the cylinder gas exchange process to be optimised for different engine speeds by changing valve opening and closing times as well as maximum valve lift. The focus of this study was the investigation of effect of the integration of the above two technologies on the performance of a gasoline engine operating at part load conditions. In this study, a 1.6 Litre in-line 4-cylinder gasoline engine is modelled on engine simulation software and simulated data is analysed to show improvements in fuel consumption, CO2 emissions, pumping losses and effects on CO and NOx emissions. A CDA and VVA operating window is identified which yields brake specific fuel consumption improvements of 10-20% against the base engine at engine speeds between 1000rpm to 3500rpm at approximately 12.5% load. Highest concentration of CO emissions was observed at between 4 to 5 bar BMEP at 4000rpm and highest concentration of NOx at the same load range but at 1000rpm.Findings based on simulation results point towards significant part load performance improvements which can be achieved by integrating cylinder deactivation and variable valve actuation on gasoline engines. Copyright © 2014 SAE International

A free-piston Stirling engine/linear alternator controls and load interaction test facility

A test facility at LeRC was assembled for evaluating free-piston Stirling engine/linear alternator control options, and interaction with various electrical loads. This facility is based on a 'SPIKE' engine/alternator. The engine/alternator, a multi-purpose load system, a digital computer based load and facility control, and a data acquisition system with both steady-periodic and transient capability are described. Preliminary steady-periodic results are included for several operating modes of a digital AC parasitic load control. Preliminary results on the transient response to switching a resistive AC user load are discussed

Engine performance characteristics and evaluation of variation in the length of intake plenum

In the engine with multipoint fuel injection system using electronically controlled fuel injectors has an intake manifold in which only the air flows and, the fuel is injected into the intake valve. Since the intake manifolds transport mainly air, the supercharging effects of the variable length intake plenum will be different from carbureted engine. Engine tests have been carried out with the aim of constituting a base study to design a new variable length intake manifold plenum. The objective in this research is to study the engine performance characteristics and to evaluate the effects of the variation in the length of intake plenum. The engine test bed used for experimental work consists of a control panel, a hydraulic dynamometer and measurement instruments to measure the parameters of engine performance characteristics. The control panel is being used to perform administrative and management operating system. Besides that, the hydraulic dynamometer was used to measure the power of an engine by using a cell filled with liquid to increase its load. Thus, measurement instrument is provided in this test to measure the as brake torque, brake power, thermal efficiency and specific fuel consumption. The results showed that the variation in the plenum length causes an improvement on the engine performance characteristics especially on the fuel consumption at high load and low engine speeds which are put forward the system using for urban roads. From this experiment, it will show the behavior of engine performance

The composite load spectra project

Probabilistic methods and generic load models capable of simulating the load spectra that are induced in space propulsion system components are being developed. Four engine component types (the transfer ducts, the turbine blades, the liquid oxygen posts and the turbopump oxidizer discharge duct) were selected as representative hardware examples. The composite load spectra that simulate the probabilistic loads for these components are typically used as the input loads for a probabilistic structural analysis. The knowledge-based system approach used for the composite load spectra project provides an ideal environment for incremental development. The intelligent database paradigm employed in developing the expert system provides a smooth coupling between the numerical processing and the symbolic (information) processing. Large volumes of engine load information and engineering data are stored in database format and managed by a database management system. Numerical procedures for probabilistic load simulation and database management functions are controlled by rule modules. Rules were hard-wired as decision trees into rule modules to perform process control tasks. There are modules to retrieve load information and models. There are modules to select loads and models to carry out quick load calculations or make an input file for full duty-cycle time dependent load simulation. The composite load spectra load expert system implemented today is capable of performing intelligent rocket engine load spectra simulation. Further development of the expert system will provide tutorial capability for users to learn from it

Modeling of a heavy duty diesel engine to ease complex optimization decisions

Engine optimization becomes more difficult every day, more and more limits regarding emissions of noxious components have to be met. Considering heavy duty marine engines such as the 6DZC from ABC there are several important instances: IMO III reduces NOx by 75% from 2021, EPA reduces NOx by 70% from 2016. Therefore very complex systems are implemented, which each have multiple calibration or working parameters. Some are fixed, some can change depending on engine load and speed. An example of a fixed parameter is compression ratio, it can only be changed while building the engine. Other fixed parameters include: choice of injection nozzle (#holes, hole-diameter), bore, stroke, etc. Exhaust gas recirculation (EGR) is a parameter that can be changed continuously during operation of the engine. Typically there are other parameters present: Variable Valve Timing, injection timing, injection duration, injection pressure, secondary injection, wastegate setting(s), etc. Ideally these parameters are configured in a way that the engine emits very little harmful components and fuel consumption is very low. The most straightforward approach would be to test every parameter combination, record emission components and fuel consumption and choose the optimal parameter combination. This has to be repeated for every speed and load of the engine, which results in an engine map. This method becomes more and more expensive, both in time as in fuel consumption because every additional operating parameter increases the amount of tests exponentially. This is why engine simulation becomes inevitable. Accurate engine simulation is able to exclude regions of parameter values that are clearly infeasible and can give a good indication where engine tests are more interesting

Predictive Second Order Sliding Control of Constrained Linear Systems with Application to Automotive Control Systems

This paper presents a new predictive second order sliding controller (PSSC) formulation for setpoint tracking of constrained linear systems. The PSSC scheme is developed by combining the concepts of model predictive control (MPC) and second order discrete sliding mode control. In order to guarantee the feasibility of the PSSC during setpoint changes, a virtual reference variable is added to the PSSC cost function to calculate the closest admissible set point. The states of the system are then driven asymptotically to this admissible setpoint by the control action of the PSSC. The performance of the proposed PSSC is evaluated for an advanced automotive engine case study, where a high fidelity physics-based model of a reactivity controlled compression ignition (RCCI) engine is utilized to serve as the virtual test-bed for the simulations. Considering the hard physical constraints on the RCCI engine states and control inputs, simultaneous tracking of engine load and optimal combustion phasing is a challenging objective to achieve. The simulation results of testing the proposed PSSC on the high fidelity RCCI model show that the developed predictive controller is able to track desired engine load and combustion phasing setpoints, with minimum steady state error, and no overshoot. Moreover, the simulation results confirm the robust tracking performance of the PSSC during transient operations, in the presence of engine cyclic variability.Comment: 6 pages, 5 figures, 2018 American Control Conferance (ACC), June 27-29, 2018, Milwaukee, WI, USA. [Accepted in Jan. 2018

High-power baseline and motoring test results for the GPU-3 Stirling engine

Test results are given for the full power range of the engine with both helium and hydrogen working fluids. Comparisons are made to previous testing using an alternator and resistance load bank to absorb the engine output. Indicated power results are presented as determined by several methods. Motoring tests were run to aid in determining engine mechanical losses. Comparisons are made between the results of motoring and energy-balance methods for finding mechanical losses

Test stand performance of a convertible engine for advanced V/STOL and rotorcraft propulsion

A variable inlet guide vane (VIGV) convertible engine that could be used to power future high-speed V/STOL and rotorcraft was tested on an outdoor stand. The engine ran stably and smoothly in the turbofan, turboshaft, and dual (combined fan and shaft) power modes. In the turbofan mode with the VIGV open, fuel consumption was comparable to that of a conventional turbofan engine. In the turboshaft mode with the VIGV closed, fuel consumption was higher than that of present turboshaft engines because power was wasted in churning fan-tip air flow. In dynamic performance tests with a specially built digital engine control and using a waterbrake dynamometer for shaft load, the engine responded effectively to large steps in thrust command and shaft torque