Background
The use of non-steady pressure-gain combustors can dramatically improve efficiency. The push towards more efficient, powerful, and clean combustion engines is driving seemingly disparate engine configurations toward combustion processes where pressure waves or pulsations are either designed in or practically unavoidable. Although these innovative engines differ in mechanical design and thermodynamic principles, the combustion processes include flame-wave interactions at some stage. Incorporating constant-volume combustion in a gas turbine engine, known as the Atkinson/Humphrey cycle creates a cycle that has a higher efficiency than the traditional Brayton cycle for the same inlet state at the combustor.
The research proposed by our client focuses on the fundamentals of a novel pressure-gain combustion engine concept – the Wave Disc Generator (WDG). A Wave Disc Generator is a pressure gain device that transfers energy between gas streams of different energy density by propagating expansion and shock waves within a chamber. It does so using a constant-volume combustion system which may reduce fuel consumption of gas turbines and propulsion engines. The cycle shown in Figure 2 shows the stages that an individual chamber undergoes, where the vertical axis shows the progression of stages as the chamber rotates. By opening and closing the injection and ejection ports, hammer shock and expansion shock waves are propagated within the chamber, which increase the pressure within the chamber. This increase in pressure is then ignited to further increase the pressure within the chamber. This pre-compressed gas is then ignited to further increase the pressure within the chamber, and the gas is ejected at an extremely high pressure.
The research group will focus on the development of Wave Disk Generator technology. Due to budgetary and time limitations we have limited our scope to the very early stages of the technology. We move forward in a type of hybrid project detailed to be analytical, design oriented, with a life cycle effect of improving the Mechanical department faculty research in turbomachinery. We will undergo numerical turbomachinery analysis, structural analyses as well as computational fluid analysis. Our goal is to have a prototype set up to help test good fit of the data. Our group has decided to go about creating the fundamental concept for the WDG of pre-compression in the rotation due to rotary action and dynamic shock wave propagation.
We will build a design to show the correlations to the computational fluid analysis (CFD) our research group is doing. This design determines the CFD analysis initially so there is work between the CFD, the design as well as the manufacturing of the product. This project starts as an analytical one, has goals set in producing a prototype design, and has a farther reaching goal of setting up the path for the new research at Columbia in turbomachinery and Aerodynamics under the P.I.
Liturature Review
Using a copyright search of “shock wave engine,” the group found articles that outline the past research on wave engine technology, particularly that of Michigan State University, which is researching a wave disk engine to incorporate into a hybrid vehicle engine. ARPA-E outlines the project as one that “uses the combustion of air and fuel to build up pressure within the engine, generating a shock wave that blasts hot gas exhaust into the blades of the engine’s rotors causing them to turn, which generates electricity.” Many of the principles used in the MSU design are similar to that of the group’s design.
The group decided to continue the literature review by finding applicable patents followed by searching for journals written by the inventors named on these patents. The group searched for patents invented by the client, Professor Akbari, and his associates. The most applicable patent was Patent 7,555,891, claimed by Professor Akbari and Dr. Muller from Michigan State University. The patent described a wave rotor that is in the radial configuration with an inlet port in the center, although the axis of the fluid passageways is not oriented with the rotational axis.
Returning to our journal research, we were able to obtain a large collection of journal articles published by Dr. M.R. Nalim focusing on axially configured wave rotor internal combustion engine. These articles detailed the work done at Indiana University Purdue University Indianapolis concerning wave rotor aerothermodynamic design. The article that is most applicable to the work done by is “Wave Rotor Combustor Aerothermodynamic Design and Model Validation based on Initial Testing.” This article details numerical and computational analysis used as the foundation for its design, and it followed with experimental data correlating to the analyses that are shown in the beginning of the journal. Since the configuration is axial, there are some key differences in the analysis, but the analytical foundation created in Dr. Nalim’s articles have proven useful to the proposed design.
Preliminary Analysis
Our first Numerical analysis came from intensive research in turbomachinery and rotary engines. This figure is just a small example of the iterations done. Iterations were done for every angle of the impeller from -85 to 85 degrees from the radial direction in multiples of 5. In addition those data sets were extrapolated over several flow rates at several key motor RPM values. These numerations are for a continuous flow model or a model of a centrifugal compressor. These preliminary calculations are to be used in comparison to the shockwave calculations. We compared work produced/consumed versus outlet pressure for varying angles of the blade tip. As would be expected, the larger the work produced/consumed and pressures are for larger angles because they can fully harness the angular momentum of the disk and incorporate it into the flow.