Henrietta Project: Centrifugal Air Compression

P18473

Steven Paine Mechanical Engineering

Matt Colclough Mechanical Engineering

Nate O’Hara Mechanical Engineering

Michelle Kwong Mechanical Engineering

Multidisciplinary Senior Design Conference

Kate Gleason College of Engineering

Rochester Institute of Technology

Rochester, New York 14623

Abstract

Dresser-Rand is a global manufacturer and supplier of compressors and turbines used for oil,

gas, petrochemical, power, and process industries. The project’s objective involved finding and

buying a compressor or blower that implements centrifugal technology. This unit must then be

instrumented to measure vibration, flow rates, pressures, and temperatures at both suction and

discharge ends. This unit must be easy to disassemble for impeller and bearing replacements,

available to be purchased separately. The unit and subsequent impellers and bearings will be

subjected to condition testing in the RIT Compressor Lab and help determine potential failure

modes of centrifugal technology. During condition testing, the system will purposely be

unbalanced in order to simulate failure/fatigue of the system and subcomponents; with this in

mind, it is critical that the consumable parts to be accessible.

After benchmarking several centrifugal compressors, blowers, turbochargers, and superchargers,

it was determined that an automotive supercharger would best satisfy customer and engineering

needs, while still staying within the $5,000 budget.

A major risk that we saw was the ability to supply enough power to the motor and the ability to

discharge air out of the lab. These building modifications gated our ability to run the system. The

budget to support the originally quoted $15,000 modifications and the time constraints was what

gated us from initially moving forward.

Motivation

The original proposed design for the project was to utilize an industrial grade centrifugal

compressor, sponsored by Dresser-Rand (D-R). The customer for the Henrietta Project is Dr.

Kolodziej, an associate professor in the Mechanical Engineering Department at RIT. A few of the

quantitative customer needs include, but not limited to, a fully instrumented system that fits within

the existing lab space, a compressor utilizing centrifugal technology, and a system that has

replaceable parts available for purchase. The qualitative customer needs include, but are not

limited to, closely mimicking the operational capabilities of an industrial grade compressor, a

system design that requires minimal modifications to the lab, ease of instrumentation to the

system that measures flow, pressure vibration and temperature. The intent of the product, or

compressor is to provide valuable data of the system and wear components, such as the impeller

and bearings, from condition testing. The gathered data would potentially be used by industrial

and automotive manufacturers to improve the quality of future equipment and provide further

research. Figure 1 refers to the process flow for testing and condition of the compressor system.

Figure 1. Process flow for system testing.

For the system, an automotive supercharger was chosen to mimic a centrifugal compressor

found in industrial size, but on a scale that can fit into the lab space provided. With the

supercharger, the target customer and engineering requirements were able to be met, with the

added benefit of smaller working components and easier maintenance.

Device Utility and Novelty

The proposed design of utilizing an industrial grade centrifugal compressor was found to not be

feasible based on the limitations of the lab, which were mainly in power and space. The electric

power available to the designated lab is 240V/3ph/30A. Most industrial compressors are sized for

upwards of 10hp that would require access to at least 480V/150A power. In addition to the

electrical constraint, the $5,000 budget was vastly insufficient for the cost of an industrial

compressor, as well as the cost of the equipping the lab with the appropriate power. Another

limiting factor was space, which helped us narrow down on our selection when it came to

benchmarking. The location requirement options shown in Table 1 were mainly driven by the size

of the product. The options started out with, “In Lab”, “Not in Lab”, and “In Lab with Modifications”.

The products associated with “Not in Lab” and, later, “In Lab with Modifications” were eliminated

from our options, as we determined that instrumenting a centrifugal compressor with a “Not in

Lab” option, meaning it would be placed outside, would quickly deplete the project funds. From

the onset of MSD I, the project was tasked with finding an alternative product that still utilizes

centrifugal technology.

The initial goal was to have a product applicable within the realm of an industrial setting. After

realization an industrial scale compressor was not a feasible option, we decided to use an

automotive supercharger. By choosing an automotive supercharger, we were able to broaden the

possible applications of our project to the automotive field. The automotive supercharger was

capable of providing the desired outputs we wanted from the industrial sized compressor, but at a

cheaper price and smaller footprint. In order to make positive pressure in the exhaust pipe, a

back pressure mechanism must be placed onto the system. This was achieved with a gate value

on the discharge piping.

Table 1. Supercharger benchmarking.

Technical Feasibility

When the supercharger was decided on for the project, the key feasibility questions that were to

be answered included the following:

1. What size electrical motor will fit within the electrical constraints of the lab, yet provide

sufficient torque to the supercharger and, thus, boost?

Existing Lab Power Capacity

Voltage = 240V

Current ≤ 50A

Power = VI = 240V x 50A = 12,000W ≅ 16hp

Motor Sizing

At the outlet of the supercharger there will be a pressure rise of the inlet air. The pressure

rise is dependent on many factors including, inlet air temperature, inlet air pressure, input

torque, shaft rotational speed, mass air flow rate, and pulley step-down ratio. Each of

these variables are mapped on the compressor map, Figure 3, provided from the

supercharger manufacturer, Vortech.

Figure 2. Vortech supercharger compressor map.

The required torque at a specific pressure rise is a function of the difference in enthalpy

between the inlet and outlet, mass flow rate, isentropic efficiency and compressor speed.

2. Which supercharger units offer replacement wear components?

a. Vortech

b. Paxton

c. Third-party wear component suppliers:

i. Jegs

ii. Summit Racing

iii. Superchargersonline

3. Will the supercharger fit efficiently within the lab?

The system was able to fit within a 3’ x 6’ footprint within the lab.

4. Will the sensors have sufficient resolution to obtain data from testing?

All sensors provide resolution which satisfies customer requirements

5. What noise level will be produced from a motor spinning at speeds greater than

3000 RPM?

Noise is acceptable with hearing protection.

6. What type of enclosure will be necessary, if any?

A plexiglass and aluminum (8020) enclosure protects viewers and operators in case of

system failure.

7. What is a suitable source for intake and exhaust?

Galvanized steel HVAC piping run outdoors to provide intake and exhaust.

8. At a specific pressure rise, what can we expect the temperature to be for the

discharge air?

At 100°F intake temperature and 8psi boost, the outlet temperature would be 180°F, which

is the operational limit of the pressure sensor that we instrumented on the system.

9. What are expected lead times for compressor replacement parts?

Maximum lead time for components is two weeks, with some components being available

off-the-shelf from an auto parts store.

Budget

The proposed budget was $5,000. Originally, it seemed like this would fall short, as we found that

building modifications, including ventilation and power, were quoted to be ~$10,000. One critical

customer requirement, a 1:2 air compression ratio, was modified to having at least some

compression. This was a compromise made to meet our budget needs leaving the system with a

20hp motor instead of a 60hp motor, which will run on the existing power in the room and provide

at least 1:1.2 compression ratio. Figure 3 maps out the power and torque needed with respect to

compression ratio. From the graph, it was determined that the 20hp motor paired with a VFD

would satisfy the updated customer requirements.

Figure 3. Power and torque needed for each compression ratio

The bill of materials, Table 2, shows that the final spending amount on the project was $6,222.05.

The amount that was spent on all materials was $6,254, this includes materials that were not

used / being processed for return. Considering the whole scope of the project, $6,222.05 was not

unreasonably far from the $5,000 budget. If the Dresser-Rand centrifugal compressor had been

selected for the project, the budget would have been assuredly exceeded.

Table 2. Bill of Materials

Prototype/Implementation

Final System

The final system runs on 240V/30A power with the support of a VFD to ramp up frequency to the

motor. Measurements for temperature and pressure are taken at the inlet and outlet of the

compressor via two thermocouples and two pressure transducers. Outlet mass flow rate is found

using a mass air flow sensor. Motor speed is found using a proximity sensor that reads a

previously made set screw hole on the motor pulley. Back pressure is controlled using a PVC

gate valve; this will later be replaced by a brass gate valve with a threaded stem that allows for

more control of the opening and closing of the valve. Inlet and exhaust air is routed to and from

the system through Schedule 40 aluminum piping conjoined by silicone fittings.

Future Improvements

Future iterations of the system can be improved by:

1. Swapping the gate valve for a brass valve with a threaded stem, which would be better

suited to handling the pressure of the exhaust air

2. Outfitting the lab to provide greater power to increase compression range from the current

1:1.2 ratio to 1:2 or greater

3. Increase motor size (horsepower) with a respective VFD to provide greater compression

from inlet to outlet

Requirement Satisfaction:

Table 3. Engineering Requirements vs. Performance

Table 4. Customer Requirements vs. Performance

Acknowledgements

Special thanks to Dr. Jason Kolodziej, Bill Nowak, Dr. William Humphrey, Robert Kraynik,

Richard Wurzer, Jan Maneti, Dresser-Rand, Vortech